The present invention relates to a variable density scanner.
Variable density scanners are known in the art for scanning a continuous tone image at a desired line density In one prior art system an optical lens system is used in combination with a flying spot scanner. The lens system is located in front of the screen to focus the spot formed thereon onto the surface of an original, the focused spot size being varied by controlling the spot size of the electron beam. However, this prior art system has various shortcomings which include low power of resolution, low brightness, picture distortion, and noise.
Another prior art system comprises a variable aperture disk having a plurality of apertures for passing a light beam through one of the apertures to form a variable beam spot on an original and a control circuit which controls the scan rates of the original in the main-scan and subscan directions in accordance with the size of the beam spot. This prior art system is also unsatisfactory since the system becomes complex and the variable range of the spot size is limited.